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Chapter II Solution Growth….
large number of ionic salt crystals, organic crystals and semi-organic crystals
are grown by these methods. Various authors [2, 8, 37, 58-60] have given
elaborative discussions on various solution growth techniques and hence a
brief review is presented here.
Usually, slow cooling method is employed to achieve the required
degree of super-saturation. The simplest illustration of the method is
crystallization in a closed vessel, which is depicted in figure (2.8).
Figure:2.8 Schematic diagram of a crystallizer used for rapid crystal growth: (1)
growth tank; (2) air-sealed lead; (3) stirrer; (4) heater; (5) thermo-controller; (6) water
bath; (7) platform with the seed; (8) growth solution; (9) water cup seal.
A solution saturated at and above room temperature is poured into a
crystallizer, which is then hermetically sealed. Prior to this, the solution is
heated to a temperature slightly above the saturation point in order to avoid
spontaneous crystallization at the moment it is filled into the crystallizer. A
seeding crystal is suspended in the solution and the crystallizer is placed in a
water thermostate whose temperature is reduced according to a pre-assigned
plan. Super-saturation is maintained by slow cooling and the rates required
can be as low as 0.1 0 C to 1 0 C per day. This requires appropriate
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